1. Field of the Invention
The invention is based upon a spray head of a spraying tool for spraying of spray media, in particular of mold release agents, onto foundry molds.
Where and how the spray nozzles are positioned during the spraying operation relative to the surface to be sprayed, is of considerable influence as regards the spray quality, i.e. the quality of the release agent on the foundry mold after the spraying operation. This may be particularly problematical if the foundry mold is provided with deeply penetrating cavities. In order to meet this problematic, known spraying tools are structured in many different ways.
2. The Prior Art
In a known spray head of the kind under consideration (German Laid-open Patent Specification DE-OS 40 16 368) the adapter is formed by a connector and a spacer which are connected to each other in a T-shaped manner so that the spray plates on the reverse surface and on the upper surface are almost completely covered. While the connector of the adapter may be shorter than the spacer, the latter has to be of a length about equal to that of the spray plates in order to make possible the necessary connection between supply conduits of the adapter and the connecting conduits of the spray plates leading to the main conduits. Depending upon the foundry mold, in this known spray head, spray plates seemingly suitable as regards the foundry mold are mounted on the spacer, requiring in most instances that the spacer also be exchanged along with the connector in order to yield the requisite overlapping length. Even though the spraying tool does not only move the spray head into the mold but also moves it within the mold, especially laterally thereof, additional extension tubes which, when mounted on the spray plates, compensate for the varying distance between the spray plate and the wall of the foundry mold, are nevertheless required for the spray nozzles because of the many different configurations of foundry molds. Such extension tubes, particularly relatively long ones, are disadvantageous because when operating continuously, their preset spraying position may easily be changed. In particular, during entry of the spray head into and its withdrawal from the foundry mold, as well as during its release and storage, even slight forces acting on the extension tubes may lead to their becoming bent or displaced.
Moreover, the use of such a spray head requires maintaining a large number of spray plates and, possibly, of spacers even though selected modular structures result in shortened movements relative to the wall of the foundry mold and in the weight of the spray block.
From another spray block (German Published Patent Specification DE-AS 25 35 578 and German Patent DE-PS 37 09 666) it is known to clamp a plurality of spray plates together to form a spray head for spraying in two opposite directions, by placing the nozzles in oppositely facing front walls of these spray plates. The main conduits extend transversely of the plates, and all the branch conduits leading to the nozzles extend in the plates, throttle members being provided in the branch conduits leading to the nozzles. Since the overall length of the spray head is defined by the number of the individual spray plates and since the dimensions of the spray plates is equal to the height and depth of the entire spray head, such a spray head is relatively heavy. Also, the resulting dividing planes, or interfaces and sealing surfaces depends on the number of spray plates. The sealant usually is a gasket extending over the dividing plane and provided with recesses for the conduit connection. To attain sufficient tightness, relatively large tensional forces are required to clamp together the individual spray plates of the spray head. Because of the unchangeable depth of such a head the lateral paths to be traversed by the spraying tool are relatively long. It is, however, advantageous that the overall length of the spray head can easily be altered, albeit at the expense of its weight. In connection with such a spray head it is also known to provide spray nozzles in the broad side of the terminal plate, or to provide the core block supported by the adaptor with a minimum number of nozzles which discharge from opposite sides. In such an arrangement (DE-OS 37 41 474) spray plates may modularly be mounted to either longitudinal front side of the core block for the elongation thereof.
The sealing between adjacent plates is usually provided by gaskets which require not only a very good support surface but, because of the relatively large contact surface and the resultant low Hertz compression, also large clamping forces. The use of O-rings seated in corresponding recesses surrounding conduit ports is less common because such O-rings may easily escape and be lost when the plates are being disassembled.